Structural and electrochemical studies of undoped and In3+-doped co-binary Cu2-xTe and Bi2Te3 thin films for aqueous Na–S batteries

WO₃ electrodes coated with co-binary Cu_2-xTe and Bi₂Te₃ thin films were fabricated for sodium-sulfur (Na–S) batteries. Film fabrication was controlled by adjusting the pH of the solution and the indium doping concentration. The phases of orthorhombic CuTe and hexagonal Cu₂Te with rhombohedral Bi₂Te₃ were formed on the WO₃ electrode. After In³⁺ doping, In³⁺ ions act as Frenkel defects in the Cu_2-xTe structure. This indicated that In³⁺ ions are located at interstitial sites in the Cu_2-xTe structure with higher defect creation energy. Furthermore, more interconnected-like nanoparticles and reduced porosity were observed, thereby indicating that indium segregation with grain boundaries presented and contributed to an enhancement of the surface mobility, nucleation density, and a smoother surface. For electrochemical characteristics, a polysulfide solution was used as a redox electrolyte for ion transport. Optimization of the pH and indium concentration attributed to improve the exchange current density (J₀) and time responses for the colored and bleached states because of faster movement of Na⁺ and S²⁻ ions during inter/de-intercalation. Furthermore, optimization of the electrode by adjusting the pH and doping with indium is advantageous for both Na–S and rechargeable batteries because of long life cycle, reasonably high power and energy density of 306 W/kg and 9.35 Wh/kg, respectively. The highest specific capacity (C_s) values of the charge and discharge cycles for In³⁺-doped electrodes are ∼ 21 and 19 mAh/g, respectively with the coulombic efficiency approximates 100% (average value of ∼96%). This approach may provide a general path for the fabrication of undoped and In³⁺-doped co-binary Cu_2-xTe and Bi₂Te₃ films on WO₃ electrodes and may increase our knowledge regarding Na–S batteries for further performance improvement.     

Investigation of O2- and Air-Exposure Effects on Amorphous In–Ga–Zn–O Thin-Film Surface by X-ray Photoelectron Spectroscopy

A sputter-cleaned amorphous In–Ga–Zn–O thin-film surface was exposed to O₂ and air, and the spectral changes at the O 1s, In 3d, Ga 3d, Zn 3d, and the valence band were investigated by soft-X-ray photoelectron spectroscopy. Both exposures reduced the density of the oxygen-vacancy-representing deep subgap state, which was located above the maximum of the valence band. The exposures also reduced the densities of the metallic states, which were observed near the Fermi energy and at In 3d. A higher oxidation state than that of the unexposed metal oxide was negligibly observed at the metal 3d orbitals. These results imply that O₂ and air exposures effectively fill oxygen vacancies and decrease the number of free electrons.     

Enhanced thermoelectric efficiency of Cu2−xSe–Cu2S composite by incorporating Cu2S nanoparticles

The study of thermoelectric transport properties in Cu_2−xSe and Cu₂S has gained an importance in the thermoelectric research during last few years due to their superionic behavior and low cost. Here, we reported a facile method to enhance the thermoelectric efficiency of Cu_2−xSe by introducing Cu₂S nanoparticles (NPs) in the matrix of Cu_2−xSe. The observed efficiency is a direct result of simultaneous improvement of Seebeck coefficient (S) because of the external strain induced by Cu₂S nanoinclusions in Cu_2−xSe and decline in the total thermal conductivity by suppressing both electronic and lattice thermal contributions. Such higher S and lower thermal conductivity is realized for a composite structure with 10 wt% nanoinclusions of Cu₂S which effectively contributed to higher ZT value of 0.90 at moderate temperature of 773 K. Thus, it is believed that the proposed hybrid structure is a promising p-type thermoelectric material for mid-temperature range energy harvesting applications.     

A Significant Role of Tb2O3 on the Optical Properties and Radiation Shielding Performance of Ga2O3–B2O3–Al2O3–GeO2 Glasses

Journal of Inorganic and Organometallic Polymers and Materials - This research article focuses on the significant role of Tb2O3 content on the optical properties and radiation shielding performance...     

Ceramic varistors based on ZnO–SnO2

Model ceramic varistor formulations based on 98% ZnO–SnO₂ (plus 2% oxides of Bi, Co and Mn) were prepared by conventional powder processing routes; specimens were sintered at 1150–1275 °C. The product density increased with SnO₂ content, but decreased with increase in sintering temperature. The microstructures contained ZnO, Zn₂SnO₄ spinel and very small bismuth rich phases; with increasing Sn content the spinel became the dominant phase. From I–V measurements, the non-linear coefficients were found to be in the range 24–32. For all compositions, the α values decreased with increasing sintering temperature; the maximum α value was obtained with samples containing 20 mol% SnO₂ sintered at 1200 °C. Breakdown fields were in the range 3000–11000 V/cm and increased with increasing tin content. Leakage currents were in the range 1–11 μA. Tin substitution for Zn appears to cause a strong donor effect.     

Glass Formation and Luminescence of Glasses in the Ga2S3–GeS2–Nd2S3System

The results of spectral measurements and the differential thermal analysis (DTA) data for glasses in the Ga₂S₃–GeS₂–Nd₂S₃system are presented. The boundaries of the glass formation region in the Ga₂S₃–GeS₂–Nd₂S₃system are determined. It is shown that the luminescence efficiency increases with an increase in the gallium sulfide content due to the displacement of the concentration quenching boundary of Nd³⁺luminescence with a change in the glass matrix composition.     

一步法水相制备Cu–In–Zn–S量子点及其荧光性能

采用简单的一步法制备了水溶性Cu–In–Zn–S (CIZS)四元量子点,利用X射线衍射仪、透射电子显微镜和荧光光谱仪等测试手段研究了反应温度、阳离子浓度和前驱体溶液pH值对样品的物相组成、显微形貌以及荧光性能的影响规律。结果表明:随着反应温度的升高,量子点的结晶度逐渐提高,荧光强度显著增强,当反应温度为95℃时,荧光强度达到了最高值;随着阳离子浓度的逐渐增大,量子点的粒径逐渐减小,导致其发光峰位由634 nm蓝移至617 nm,当阳离子浓度为1.5 mmol/L时,量子点的荧光强度最高。此外,当溶液pH值=5.0时,配体对量子点的表面钝化效果最佳,荧光强度达到最高值。红外光谱表明,量子点表面存在多种功能基团,赋予了量子点优异的水溶性,因此在生物成像领域具有广阔的应用前景。     

Electroconductivity and Electrode Properties of Amorphous PbS–Ag2S–As2S3 and PbS–AgI–As2S3 Films Deposited from Solutions of Glass in n-Butylamine

Glass Physics and Chemistry - The parameters of the specific electroconductivity and electrode properties of massive glass and amorphous films of PbS–AgI–As2S3 and...     

Survey on Langmuir–Blodgett Films of Polymer and Polymeric Composite

This article presents a concise review of research performed in the field of Langmuir–Blodgett films. Various types of conducting polymers, piezoelectric/pyroelectric polymers, and ferroelectric polymers have been utilized for fabrication of polymeric and composite Langmuir–Blodgett films. The Langmuir–Blodgett polymers may reveal fine Langmuir–Blodgett behavior such as mechanical robustness, heat resistance, and chemical stability. Moreover, polymers offer recompenses of synthetic tailoring, low-cost, and volume production toward enhanced performance Langmuir–Blodgett materials. The applications of Langmuir–Blodgett films have been reviewed in sensors, electroluminescence devices, polymeric light-emitting diode, and microelectronic devices. Langmuir–Blodgett films represent exciting area of materials science demanding recent research attention.     

Effect of solid loading on properties of Y2O3–Al2O3–Nd2O3 powder mixtures obtained by planetary ball milling and ceramics based on them

The effect of the solid loading (41–50 wt%) of the slurry on granulometric composition and physico-chemical characteristics of Y₂O₃–Al₂O₃–Nd₂O₃ powder mixtures obtained by planetary ball milling has been studied for the first time. It was shown that the particle size distribution of powder, its Zeta potential, and specific surface area depend on the solid loading of the milled slurry and, consequently, on the interparticle distance during milling. The interparticle distance decreases from 200 nm to 142 nm with an increase of solid loading in the range of 41–50 wt%. It was shown that for the solid loading of 47 wt%, the convergence of particles to a distance comparable to their median diameter promotes subsequent clustering of particles. This facilitates the sintering of highly-homogenous ceramics. It was found that solid loadings in the 46–50 wt% range is useful for obtaining high-quality Nd:YAG transparent ceramics. The lowest optical losses optical losses of 1 × 10^?3 cm^?1 and the highest in-line transmittance of 84.1%@1064 nm were obtained for 1 at.% Nd:YAG transparent ceramics (22 × 3 × 4 mm³) prepared from slurries with 47 wt% solid loading (taking all other ball milling parameters fixed). If the interparticle distance in the powder is higher (solid loading of 41 wt%) than the median particle diameter, the ceramics are characterized by significant residual porosity due to the survival of large particles (insufficient milling).     

Symmetric supercapacitors based on copper–antimony chalcogenides: A trade-off between S and Se

To enable a society based on carbon-free electricity, electric energy storage is crucial. In this regard, the development of novel supercapacitors with high capacity and long cycling stability is critical as supercapacitors have a higher power density than batteries. A promising group of supercapacitors is chalcogenide-based materials as they show excellent ionic conductivity and stability. Moreover, ternary chalcogenides are earth-abundant, low-cost, non-hazardous materials, and the third constituting element can optimize the structural and electrochemical properties leading to improved performances. However, so far, only a few ternary chalcogenide-based supercapacitors have been developed. Herein, we have synthesised and characterized Cu₃Sb(S/Se)₄, Cu₉S₅, and Cu_2-xSe using the same solution-based method at 150°C. We compare the electric properties of all four compounds to check their suitability as supercapacitor electrode materials. The highest capacitance and cyclic stability is found for Cu₃SbS₄. Notably during CV studies, very high specific capacitance of 397 F/g was recorded at 5 mV/s. Motivated by this result, a coin cell based on Cu₃SbS₄ is developed showing 21 F/g at a current rate of 0.5 A/g with excellent cyclic stability.     

Effect of Al Content on the Isomerization Performance of Solid Superacid Pd–S2O82−/ZrO2 –Al2O3

The effect of Al content on the performance of the Pd–S₂O₈²⁻/ZrO₂ –Al₂O₃ solid superacid catalyst was studied using n-pentane isomerization as a probe reaction. The catalysts were also characterized by X-ray diffraction (XRD), Fourier transform Infrared (FTIR), specific surface area measurements (BET), thermogravimetry–differential thermal analysis (TG–DTA), H₂-temperature programmed reduction (TPR) and NH₃ temperature-programmed desorption (NH₃-TPD). The Pd–S₂O₈²⁻/ZrO₂ –Al₂O₃ catalyst made from Al₂O₃ mass fraction of 2.5% exhibited the best performance and its catalytic activity increased by 44.0% compared with Pd–S₂O₈²⁻/ZrO₂. The isopentane yield reached 64.3% at a temperature of 238 °C, a reaction pressure of 2.0 MPa, a space velocity of 1.0 h ^− 1 and a H₂/n-pentane molar ratio of 4.0. No obvious catalyst deactivation was observed within 100 h.     

High-temperature multilayer actuators based on CuO added BiScO3–PbTiO3 piezoceramics and Ag electrodes

High-temperature multilayer actuators based on Cu doping 0.367BiScO₃–0.633PbTiO₃ ceramic slices and Ag electrodes were prepared by low-temperature co-firing technology. The 0.3 wt% CuO addition has effectively reduced the sintering temperature of the ceramic from ~1080 to 930°C, thus the multilayer actuator were sintered at 930°C which is lower than the Ag melting point, that is, 961°C. The 4.3 mm thick multilayer actuator is composed of a series of ~44-μm-thick ceramic slices and ~2-μm-thick Ag electrodes. As a result, a ≥0.13% strain with nm-scale preciseness can be produced in the actuator by 200 V driving voltage not only at room temperature but also at a high temperature up to 200°C. This actuator is essential for industrial machinery that requires nm-scale position control at 20-200°C.     

Porous ceramics based on high-thermal-stability Al2O3–ZrO2 nanofibers for thermal insulation and sound absorption applications

Al₂O₃ fibers are promising candidates for porous ceramics, but the sudden growth of grains in the fibers above 1200 °C will limit their applications for high temperature. Herein, we reported the successful fabrication of the Al₂O₃–ZrO₂ nanofibers by electrospinning and the nanofiber-based porous ceramics by a combination of gel-casting, freeze-drying and high-temperature sintering. Results show that the addition of Zr could greatly improve the thermal stability (up to 1400 °C) of the Al₂O₃-based nanofibers, owing to the inhibition of the sudden growth of the grains in the fibers at high temperature. The Al₂O₃–ZrO₂ nanofiber-based porous ceramics after sintering at 1100–1400 °C possessed a multi-level pore structure and exhibited high thermal stability, ultra-high porosity (97.79–98.04%), ultra-low density (0.075–0.091 g/cm³) and thermal conductivity (0.0474–0.0554 W/mK), and excellent sound absorption performance with the average sound absorption coefficient of 0.598–0.770. These porous ceramics are expected to be employed in the fields of high-temperature thermal insulation and sound absorption.     

Growth of In2O3 Nanowires Catalyzed by Cu via a Solid–Liquid–Solid Mechanism

In₂O₃ nanowires that are 10–50 nm in diameter and several hundred nanometers to micrometers in length have been synthesized by simply annealing Cu–In compound at a relatively low temperature of 550°C. The catalysis of Cu on the growth of In₂O₃ nanowires is investigated. It is believed that the growth of In₂O₃ nanowires is via a solid–liquid–solid (SLS) mechanism. Moreover, photoluminescence (PL) peaks of In₂O₃ nanowires at 412 and 523 nm were observed at room temperature, and their mechanism is also discussed.     

Enhanced photocatalytic and antifungal activity of ZnO–Cu2+and Ag@ZnO–Cu2+ materials

Zinc oxide is one of the most versatile nanostructured materials with a broad range of applications. Besides, its physicochemical properties can be tuned easily by synthesis conditions to be optimal for a specific application. In our group, we aim for the production of visible light-active materials with enhanced antimicrobial activity. Thus, we synthesize ZnO–Cu²⁺and Ag@ZnO–Cu²⁺ by using a fast and robust microwave solvothermal reaction. We investigate the limit of solubility of Cu²⁺into ZnO lattice producing Cu doped ZnO materials with different doping levels (1, 2, 3, 4, and 5 at. %, Cu/Zn). We also investigate the role of the copper precursor, using copper(II) acetate or copper(II) sulfate as model precursors. Copper acetate incorporates more efficiently into ZnO lattice by decreasing the Eg value of the doped materials at low doping levels. Furthermore, we study the composites Ag@ZnO–Cu²⁺ aiming to reduce doping levels and to improve antimicrobial activity. Characterization of the materials by different techniques demonstrates their uniform size, purity, crystallinity, and visible light activity. In this study, we evaluate airborne fungal contamination and demonstrate the capacity of ZnO–Cu²⁺ and Ag@ZnO–Cu²⁺ to inhibit fungal growth. We studied the microbiological quality of indoor air (vivarium) by sampling air under different conditions. By sampling air with a photocatalytic prototype, the amount of fungi in the air decreases considerably, particularly fungi that can enter the lung. In addition, ZnO–Cu²⁺ shows excellent antifungal activity against Candida sp at low doses. We use Atomic force microscopy (AFM) and holotomographic microscopy (HTM) to provide further evidence on the capacity of the prepared materials to achieve effective damage to fungal cells and to inhibit biofilm formation.     

A new 3D Keggin-POM based metal–organic framework of Cu and H2biim: Assembly and properties of fluorescence and electrochemistry

A new 3D Keggin-based metal–organic framework consisting of two kinds of Cu-H₂biim chains, Cu₁₀(H₂biim)₁₀(PW₁₂O₄₀)₂(OH)₄·5H₂O 1 (H₂biim = 2,2′-biimidazole), has been synthesized under hydrothermal conditions. The TGA and PXRD measurements show that the framework is stable after removal of the guest water molecules. In addition, the luminescent and electrochemical properties of 1 have also been investigated.     

Deuterium tracer studies on hydrotreating catalysts. 3. Influence of nickel on the rates of H2–D3 and H2S–D2 isotopic exchange

The H–D isotopic exchange between H₂ and D₂ and between H₂S and D₂ was carried out at 80°C in a recycling reactor over a series of presulfided Mo/Al₂O₂ catalysts containing different amounts of nickel. Whatever the pretreatment procedure, it was found that the promoter had no significant effect on the rate of H–D exchange or on the amount of exchangeable hydrogen present on the catalysts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Oxygen-enhanced water gas shift on ceria-supported Pd–Cu and Pt–Cu bimetallic catalysts

Aiming at enhancing H₂ production in water gas shift (WGS) for fuel cell application, a small amount of oxygen was added to WGS reaction toward oxygen-enhanced water gas shift (OWGS) on ceria-supported bimetallic Pd–Cu and Pt–Cu catalysts. Both CO conversion and H₂ yield were found to increase by the oxygen addition. The remarkable enhancement of H₂ production by O₂ addition in short contact time was attributed to the enhanced shift reaction, rather than the oxidation of CO on catalyst surface. The strong dependence of H₂ production rate on CO concentration in OWGS kinetic study suggested O₂ lowers the CO surface coverage. It was proposed that O₂ breaks down the domain structure of chemisorbed CO into smaller domains to increase the chance for coreactant (H₂O) to participate in the reaction and the heat of exothermic surface reaction helping to enhance WGS kinetics. Pt–Cu and Pd–Cu bimetallic catalysts were found to be superior to monometallic catalysts for both CO conversion and H₂ production for OWGS at 300 °C or lower, while the superiority of bimetallic catalysts was not as pronounced in WGS. These catalytic properties were correlated with the structure of the bimetallic catalysts. EXAFS spectra indicated that Cu forms alloys with Pt and with Pd. TPR demonstrated the strong interaction between the two metals causing the reduction temperature of Cu to decrease upon Pd or Pt addition. The transient pulse desorption rate of CO₂ from Pd–Cu supported on CeO₂ is faster than that of Pd, suggesting the presence of Cu in Pd–Cu facilitate CO₂ desorption from Pd catalyst. The oxygen storage capacity (OSC) of CeO₂ in the bimetallic catalysts indicates that Cu is much less pyrophoric in the bimetallic catalysts due to lower O₂ uptake compared to monometallic Cu. These significant changes in structure and electronic properties of the bimetallic catalysts are the result of highly dispersed Pt or Pd in the Cu nanoparticles.     

A high-performance asymmetric supercapacitor based on carbon and carbon–MnO2 nanofiber electrodes

An asymmetric supercapacitor with high energy and power densities has been fabricated using MnO₂/carbon nanofiber composites as positive electrode and activated carbon nanofibers as negative electrode in Na₂SO₄ aqueous electrolyte. Both electrode materials are freestanding in nature without any conductive additives or binders and exhibit outstanding electrochemical performances. The as-assembled asymmetric supercapacitor with optimal mass ratio can be operated reversibly over a wide voltage range of 0–2.0 V, and presents a maximum energy density of 30.6 Wh kg⁻¹, which is much higher than those of symmetric supercapacitors. Moreover, the supercapacitor exhibits excellent rate capability (high power density of 20.8 kW kg⁻¹ at 8.7 Wh kg⁻¹) and long-term cycling stability with only 6% loss of its initial capacitance after 5000 cycles. These attractive results make these freestanding materials promising for applications in aqueous electrolyte-based asymmetric supercapacitors with high energy and power densities delivery.